Schottky barrier lowering due to interface states in 2D heterophase devices

TL;DR

This paper demonstrates that interface states at 2D metal-semiconductor junctions significantly reduce the Schottky barrier height, affecting charge transport, as shown through ab-initio calculations on MoTe2 monolayers.

Contribution

It reveals the role of interface states originating from the metallic phase in lowering the Schottky barrier in 2D heterophase devices, contrasting with Fermi level pinning.

Findings

Interface states cause large tunneling currents.

Schottky barrier can be reduced to 55 meV.

Interface states originate from the metallic phase.

Abstract

The Schottky barrier of a metal-semiconductor junction is one of the key quantities affecting the charge transport in a transistor. The Schottky barrier height depends on several factors, such as work function difference, local atomic configuration in the interface, and impurity doping. We show that also the presence of interface states at 2D metal-semiconductor junctions can give rise to a large renormalization of the effective Schottky barrier determined from the temperature dependence of the current. We investigate the charge transport in n- and p-doped monolayer MoTe$_2$ 1T'-1H junctions using ab-initio quantum transport calculations. The Schottky barriers are extracted both from the projected density of states and the transmission spectrum, and by simulating the IT-characteristic and applying the thermionic emission model. We find interface states originating from the metallic 1T' phase rather than the semiconducting 1H phase in contrast to the phenomenon of Fermi level pinning. Furthermore, we find that these interface states mediate large tunneling currents which dominates the charge transport and can lower the effective barrier to a value of only 55 meV.